| ~(40)Ar/~(39)Ar geochronology of the Faku tectonites:Implications for the tectonothermal evolution of the Faku block,northern Liaoning |
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| 作者姓名： | ZHANG Xiaohui WANG Hui & LI Tiesheng Key Laboratory of Lithosphere Tectonic Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China |
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| 作者单位： | ZHANG Xiaohui，WANG Hui & LI Tiesheng Key Laboratory of Lithosphere Tectonic Evolution，Institute of Geology and Geophysics，Chinese Academy of Sciences，Beijing 100029，China |
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| 摘 要： | As for the metamorphic rock series distributed on the “Faku Faulted Convex (FFC)”1] of the northern Liaoning, the earliest geologic investigation divided it into the Langzishan, Dashiqiao and Gaixian forma-tions1) and considered it to be equivalent to the Liaohe Group in the eastern Liaoning, whereas Liaoning Bu-reau of Geology and Mineral Resources (LBGMR) included it into the Lower Proterozoic basement1]. Recent 1︰50000 scale geological mapping2) reveals that this deformed and …
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40Ar/39Ar geochronology of the Faku tectonites: Implications for the tectonothermal evolution of the Faku block, northern Liaoning |
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| ZHANG Xiaohui,WANG Hui & LI Tiesheng Key Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing ,China.~(40)Ar/~(39)Ar geochronology of the Faku tectonites:Implications for the tectonothermal evolution of the Faku block,northern Liaoning[J].Science in China(Earth Sciences),2005,48(5). |
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| Authors: | ZHANG Xiaohui WANG Hui Li Tiesheng |
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| Institution: | Key Laboratory of Lithosphere Tectonic Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | For lack of reliable isotopic chronological data, the metamorphic rock series in the Faku region of northern Liaoning has long been regarded as the platform basement. Recent studies reveal that these deformed and metamorphosed rocks, with a variety of protoliths of plutonic intrusions and supracrustal volcanic and sedimentary rocks, were genetically related to later ductile shearing events, and they, together with the syntectonic intrusions, constituted the large-scale Faku tectonites. In this paper, we report new 40Ar/39Ar data on hornblende, biotite, and K-feldspar from typical granitic mylonites in this suite of tectonites. The plateau age 256 Ma of FK53 hornblende and the high-temperature plateau age 262 Ma of Fk51-1 biotite should rep- resent the cooling ages when the granites, formed as a result of Paleozoic oceanic crustal sub- duction beneath the continental crust or collision of multiple micro-continental blocks, were ex- humed into shallow crustal levels. The plateau age 231 Ma of FK51-1 boitite and the apparent age 227 Ma of Fk51-2 K-feldspar are interpreted to record the time of ductile deformation occur- ring under greenschist facies conditions, i.e. the formation age of the Faku tectonites, while the age gradient from 197 Ma to 220 Ma of Fk51-2 K-feldspar probably record the subsequent stable uplift-cooling process. The tectonic exhumation event indicated by the plateau age 180 Ma of Fk51-2 K-feldspar may be associated with the onset of paleo-Pacific subduction beneath the North China plate. In addition, the U-Pb dating of FK54 zircon from later-intruded granite yields the age of crystallization of this super-unit intrusion at 159 Ma, thus establishing an upper limit for the formation age of the Faku tectonites, while the plateau age 125 Ma of Fk54 K-feldspar most likely corresponds to the rapid cooling and tectonic denudation event associated with the final collision between the Siberian plate and the North China plate. These isotopic ages provide im- portant geochronological constraints for re-evaluating the tectonic essence of the Faku Faulted Convex and ascertaining the suturing boundary between the North China Platform and the Xingmeng Fold System. |
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| Keywords: | northern Liaoning tectonite 40Ar/39Ar age zircon U-Pb age Faku Faulted Convex |
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